A vehicle occupant safety apparatus including an inflatable air bag is disclosed in U.S. Pat. No. 3,723,205. The safety apparatus includes a container which holds air under pressure. The safety apparatus also includes a gas generating material and an igniter for igniting the gas generating material. The igniter is an electrically actuated squib. When the air bag is to be inflated, the squib is electrically actuated to ignite the gas generating material. As the gas generating material burns, the pressure in the container is increased due to the gases and heat provided by burning of the gas generating material. When a predetermined elevated pressure is reached, a burst disc is ruptured to enable gas to flow from the container to the air bag.